The 130-500 GHz rotational spectrum of 2-cyanopyrimidine

The rotational spectrum of 2-cyanopyrimidine has been obtained from 130 GHz to 500 GHz. Over 7500 vibrational ground-state transitions have been assigned and least-squares fit to partial octic, A- and S-reduced Hamiltonians with low error (afit = 36 kHz). The two lowest-energy fundamental modes, the out-of-plane (v18) and in-plane (v27) nitrile bending modes, form a Coriolis-coupled dyad similar to the analogous fundamental states of other cyanoarenes. The coupled dyad was least-squares fit to a partial octic, A-reduced Hamiltonian (afit = 47 kHz) with over 6700 transitions for each vibrational state, including transitions that are perturbed or involved in resonances, as well as symmetry-allowed nominal interstate transitions resulting from Coriolis coupling. The spectroscopic information from these transitions enabled the determination of a highly precise energy separation (Delta E18,27 = 38.9673191 (77) cm-1) and six Coriolis-coupling coefficients (Ga, GaJ, GaK, GaJJ, Fbc, and FbcK ). The spectroscopic constants and transitions presented in this work provide the foundation for future radioastronomical searches for 2-cyanopyrimidine.

Automated summary

The rotational spectrum of 2-cyanopyrimidine was analyzed using 130 GHz to 500 GHz measurements. Over 7500 vibrational ground-state transitions were identified and fitted using least-squares fit to partial octic, A- and S-reduced Hamiltonians with low error (afit = 36 kHz). The study focused on the Coriolis-coupled dyad formed by the out-of-plane (v18) and in-plane (v27) nitrile bending modes, which were fit using a partial octic, A-reduced Hamiltonian (afit = 47 kHz) with over 6700 transitions for each vibrational state. The obtained spectroscopic constants and transitions have important implications for future radioastronomical searches for 2-cyanopyrimidine.